Vale, which is the world's top iron ore miner, said the report was misleading as there was no evidence of imminent risk.

The collapse of the dam was the second major mining disaster in the region since 2015, when a nearby dam co-owned by Vale collapsed.

Analysis:

Daniel Gallas, South America business correspondent

In the aftermath of the 2015 Vale disaster, Brazilian authorities were severely criticised for being too slow and complacent. No one has yet been sentenced for that accident.

This time judges, investigators and politicians are showing a different attitude. This month 17 employees have already been detained for questioning. Court orders are suspending some of Vale's most profitable operations and freezing the company's assets.

Vale's answer to both accidents is drawing the ire of the Brazilian public as was clear from a disastrous appearance by Vale chief executive, Fabio Schvartsman, at a Congressional hearing on Thursday.

The executive was evasive when questioned about why the company had not yet paid many fines regarding the 2015 disaster.

At one point Mr Schvartsman said Vale "is a Brazilian jewel" and "cannot be condemned for an accident that happened in one of its dams - even though it was such a big tragedy", drawing angry replies from lawmakers.

The company's failure to respond adequately is increasing the charge from authorities. Politicians will set up a Congress inquiry about Vale in the coming days. Stricter mining legislations are also under consideration.